Research Grants Council of the Hong Kong Special Administrative Region

HKU743907H

Wellcome Trust of the United Kingdom

082498/z/07

Funding Information:

This research was supported by grants from the Research Grants Council of the Hong Kong Special Administrative Region (HKU743907H) and the Wellcome Trust of the United Kingdom (082498/z/07). Funders' website: http://www.ugc.edu.hk/eng/rgc/index.htm,http://www/wellcome.ac.uk/. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.